linux-kernel - Re: [PATCH 16/61] KVM: x86: Encapsulate CPUID entries and metadata in struct

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Date:   Tue, 25 Feb 2020 00:12:22 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 16/61] KVM: x86: Encapsulate CPUID entries and metadata in struct

Sean Christopherson <sean.j.christopherson@...el.com> writes:

> On Fri, Feb 21, 2020 at 03:58:47PM +0100, Vitaly Kuznetsov wrote:
>> Sean Christopherson <sean.j.christopherson@...el.com> writes:
>> 
>
>> > +			if (!entry)
>> >  				goto out;
>> >  		}
>> >  		break;
>> > @@ -802,22 +814,22 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
>> >  	return r;
>> >  }
>> >  
>> > -static int do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 func,
>> > -			 int *nent, int maxnent, unsigned int type)
>> > +static int do_cpuid_func(struct kvm_cpuid_array *array, u32 func,
>> > +			 unsigned int type)
>> >  {
>> > -	if (*nent >= maxnent)
>> > +	if (array->nent >= array->maxnent)
>> >  		return -E2BIG;
>> >  
>> >  	if (type == KVM_GET_EMULATED_CPUID)
>> > -		return __do_cpuid_func_emulated(entry, func, nent, maxnent);
>> > +		return __do_cpuid_func_emulated(array, func);
>> 
>> Would it make sense to move 'if (array->nent >= array->maxnent)' check
>> to __do_cpuid_func_emulated() to match do_host_cpuid()?
>
> I considered doing exactly that.  IIRC, I opted not to because at this
> point in the series, the initial call to do_host_cpuid() is something like
> halfway down the massive __do_cpuid_func(), and eliminating the early check
> didn't feel quite right, e.g. there is a fair amount of unnecessary code
> that runs before hitting the first do_host_cpuid().
>
> What if I add a patch towards the end of the series to move this check into
> __do_cpuid_func_emulated(), i.e. after __do_cpuid_func() has been trimmed
> down to size and the early check really is superfluous.
>

Works for me, thanks!

-- 
Vitaly